In Geometry, we regularly deal with shapes. Sometimes special tools are needed to both measure and transform these shapes. Here is a list of names and pictures of the Geometry instruments, or Geometry tools as they are also known, and how they are used. This will cover the following:

- A protractor
- A ruler
- A compass
- A divider
- A set Square

**Protractor**

The protractor is a semicircular disk used to measure the angles of shapes. It is graduated from zero to 180 degrees and, therefore, can measure the angle of any two intersecting lines or vertices within this range.

However, we can also get circular protractors, which allow us to measure the degrees in a reflex angle (between 180 degrees and 360 degrees). However, semicircular protractors are often more commonly used because, through deduction and calculation, we can establish a reflex angle by detracting the acute angle from 360 degrees.

**Things to remember when using a protractor:**

- Line up the start of the angle with the first line on the protractor.
- If we are measuring the angle from the left side, use the outer readings on the protractor. If we are reading from the right, use the inner lessons.

**Ruler**

The ruler, also known as a straightedge or a line gauge, is one of the most important and obvious Geometry instruments. It allows us to draw a straight line and measure numerous objects. Sometimes rulers contain both metric and customary units for ease of measurement.

The little marks between the larger centimeter marks are called hash marks. You can see how they get their name in this picture, representing millimeters.

**Things to remember when using a ruler:**

- For an accurate reading, always measure from the zero hash mark.
- Read the measurement directly above the ruler to avoid getting a perplex error, an inaccuracy caused by reading a size from an angle.

**Compass**

The compass is a Geometry instrument that is incredibly useful for constructing shapes. For example, it can be used to draw circles and trace arcs. The distance between the pointer and the pencil is adjustable and can be changed to line up with measurements on a ruler, allowing us to create circles with specific dimensions.

It can also intersect line segments or find the midpoint of different shapes.

**Divider**

This Geometry instrument is much like a compass without a pencil. Instead, two-pointers are adjustable, allowing us to compare distances easily.

**Set Square**

A set square is a piece of equipment used to draw lines and shapes. It’s a great way to see whether a body has a right angle, as a set square always has a corner with 90 degrees.

They can also be used with rulers to create parallel lines with particular distances between them.

**Who created Geometry instruments?**

The creation of Geometry instruments is down to the efforts of a large collection of mathematicians, philosophers, and engineers over thousands of years.

The Greek mathematician, Euclid, is considered the founding father of Geometry and is often credited with solidifying the Geometry fundamentals (or postulates) that are still used today. However, his work was influenced by Egyptian mathematicians, who created tools that allowed them to construct huge skyscrapers such as the pyramids.

Then mathematicians such as William Bedwell created the ruler in the 17th century. Later, Joseph Huddart, an American naval captain, made the protractor at the start of the 19th century to navigate the sea.